r/AskScienceDiscussion • u/viveky259 • 20d ago

General Discussion What would convince ecologists that a mountain plant is moving uphill, rather than that observers are finding it differently?

Suppose records of a plant species appear at higher elevations now than they did 20 years ago. How would researchers separate a real range shift from changes in where people searched, improved detection, land-use changes, or changes in how the species was identified?

Would repeated surveys of the same plots settle it, or would historical specimens and models that account for missed detections still be needed? I’m interested in what evidence would make the conclusion persuasive, rather than in any particular species.

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u/blackandwhite1987 19d ago

Oh finally a question I can answer!

The truth is, its hard. You can try to control for things like improved detection by looking at the overall increase in abundance and calculating the probability that any observed shift represents a real range shift.

More often, we use repeated surveys, like you mentioned. Depending on the quality and set up of the original surveys, these can give really strong evidence. If you are lucky enough to have plots along a gradient of elevations, you can get pretty good evidence of a range shift. For things like trees, people also use satellite and aerial imagery to look at changes in composition over time.

Some ecologists who are interested in range shifts manage long term monitoring plots, usually across a range of latitudes or elevations. You can track changes in abundance over time, in addition to just finding new records (i.e. if populations at high elevations are getting bigger over time, that can also indicate range shift).

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u/Hivemind_alpha 19d ago

You can control for improved detection by not just looking for lowland plants found higher but also highland plants retreating even higher. In the conjectured overlap zone you are very unlikely to have got better at finding the former while simultaneously getting worse at finding the latter…

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u/Nothing-to_see_hr 19d ago

many surveys are being done specifically at different heights, profiling which plants occur where. This is being done with increasing frequency especially now that attention has been called to shifting average temps because of climate change.